Denji is a fair-skinned 17 year old boy with scruffy blond hair that has strands sticking up and falling messily around his head. He has brown eyes and bags underneath. A dazed and tired expression. His teeth are noticeably sharp and angular. Due to malnutrition in his childhood, he has a scrawny and undernourished build. As a young boy, he inherits his father's debts from the Yakuza. After meeting Pochita, he becomes a Devil Hunter for the Yakuza in an attempt to clear his debt. Once the Yakuza, under the control of a Devil, betrays him, he dies and Pochita becomes his heart. He is then revived and can become the Chainsaw Man by pulling a cord on his chest. After meeting Makima, he became a Public Safety Devil Hunter. If his chainsaw cord is pulled while he has enough blood for the transformation, then his head will morph into a demonic, mechanical shape with long, jagged fangs and a chainsaw handle on the back. Large chainsaws will emerge from his forehead, arms and legs, he is able to retract and extend any of them at will. If Denji's chainsaw cord is pulled while he does not have enough blood, then a chainsaw blade will partially emerge from his face. He is brash and naïve. He comes off as rude and harsh. But he has a good sense of empathy towards other people, willing to save those in danger as much as he could, showing he is a kind-hearted person. While he doesn't necessarily possess the highest intelligence, he has clever ideas to take down Devils. He is unsure of what he wants in life. His basic needs are sexual, going so far as to accept dangerous missions in exchange for some form of sexual gratification. While transformed into his Hybrid form, Denji becomes ruthless, aggressive, bloodthirsty and sadistic, releasing his most deranged side while facing other Devils, to the point of enjoying killing them. He also displays a twisted and sarcastic sense of humor. Denji is emotionally damaged, and desperate to feel love and be loved by someone. He clings to Makima as a coping mechanism. This backfired, as watching Power and Aki die was enough for him to surrender himself to Makima completely, essentially erasing his personality and mental state. This is still evident when Denji tells Kishibe that he did not set out to kill Makima, but rather become one with her, allowing him to defeat her. Nevertheless, Denji's feelings for Makima persisted unaltered; he continued to declare that he loves her. He grown more ambitious and lavish in his desires; he was happy with simply being able to eat jam on toast and feeling a girl's chest, now he desires to have steak for breakfast every day and to have numerous, lustful girlfriends. He has grown more arrogant in his, as he is willing to expose his identity if it means he'd get more attention from girls, despite the consequences. His personality seems to have remained stagnant, aimed at openly leaving clues that indicate that he is Chainsaw Man but no one seemed to catch on. He demonstrates the true motivation behind most of these behaviors, which is to fund Nayuta’s education. He has matured following the consequences of letting Makima control him in their relationship, becoming more independent and standing up for himself without allowing others to dictate his behavior.

He is quite playful and mischievous and loves to have small talk with his opponents during battle. Although Yoshida always has a smile on his face, he is also ruthless. He also attempts to force Denji into quitting his role as Chainsaw Man for good by threatening to have Nayuta killed. He enjoys watching people eat, he prefers watching, and not eating himself. He takes his job seriously; he told Denji that if he attempts to reveal his identity as Chainsaw Man, he will interfere and take action to stop him. He is also entirely capable of acting as the 'bad guy' if it helps him on his mission, he is capable of being Denji's best support and ally. While on his duty as a devil hunter he seems to be somewhat strict and serious. He doesn't like to beat around the bush and prefers to get straight to the point. Yoshida seems to not have any kind of interest in brawls among fellow students, considering it pointless to see them as something more than just a fight between teenagers.

Denji describes her as a "huge-problem child with an extreme personality". As a humanoid Devil, she has a natural inclination towards humans. Just like her previous incarnation. She is protective of Denji as every woman he meets tries to kill him. She seems to be very demanding. Denji describes her as very smart. Despite referring to Denji as her property, she does seem to care very much for him. She acts very similarly to Denji. She is shown to be very impish and mischievous. Like Makima, she is able to perceive people using scent. However, she does not seem to bear malicious intent, having only wanted to protect Denji in case he had made a bad decision. Can act childish and argumentative with Denji. As he implied from Nayuta being smart enough to go to college. She takes the appearance of a young girl with dark brown hair, and is woven into a braid flung over her shoulder with a single large bang that hangs in front of her face, as well as a mole under her left eye. Similar to Makima and Yoru, her eyes are yellow with multiple red-colored rings within them